How to Tell Anthrax From Flu

July 29, 2004 -- Victims of anthrax bioterror attacks can survive if they get early treatment. Now there's crucial new information on what early anthrax symptoms look like.

Just 2 pounds of bioweapon-grade anthrax, dispersed over a city of 10 million, could kill 100,000 people, according to the Procedings of the National Academy of Sciences. In this unlikely event, there probably wouldn't be any advance warning. In a day or so, many people would come down with a flu-like illness. But until that illness suddenly got worse -- and people started dying -- nobody would suspect anthrax.

But there are differences between inhalation anthrax and flu-like illness, report Demetrios N. Kyriacou, MD, of Chicago's Northwestern University, and colleagues. They compared 47 cases of inhalation anthrax -- including 11 cases of bioterror-related anthrax -- with 376 age-matched patients who went to emergency rooms with flu-like illnesses and pneumonia.

"Several clinical characteristics were more frequent in individuals with inhalational anthrax than in either the community-acquired pneumonia or influenza-like illness controls," Kyriacou and colleagues write in the July 31 issue of The Lancet.

The early symptoms of inhalation anthrax not usually seen in flu-like illness are:

Not every patient with inhalation anthrax has all these symptoms. These symptoms may be very subtle -- or even absent -- early in the course of a person's illness.

Fortunately, Kyriacou's team found that a chest X-ray quickly shows who has inhalation anthrax and who doesn't. Anthrax victims' chest X-rays always show a peculiar pattern that's seen in less than 30% of pneumonia patients and in less than 5% of patients with flu-like illness.

In an editorial accompanying the study, University of Toronto anthrax expert Jeremy Mogridge, PhD, notes that rapid identification of anthrax-attack victims could save many lives.

However, he warns that it won't be very useful to know that people have anthrax if hospitals aren't ready to care for them.

"A strong health care system with a capacity to absorb a sudden surge of patients will dramatically reduce the impact of an attack," Mogridge writes.